If you got a Mac (and that's the platform it's only running on) and if you're using iTunes to listen to your music you probably want to give this Dashboard Widget a try - it automatically searches the music video which supposedly belongs to the music you're currently listening to and plays it in a small window on the dashboard:

"YouTube has stacks and stacks of music videos on their website. I have written a little dashboard widget called iTube. iTube gets the artist and title of the song you are playing in iTunes. It then performs a search on youtube and plays the first hit in the widget window. Once installed iTube works by itself in the background, so start a song up iTunes then look at your dashboard and with a little luck you’ll be watching what you are listening to."

Source: http://philipandrews.org/blog/itube/